Typically, sound systems for live concert touring are owned by a professional sound provider and travel in one of many tractor/trailer trucks with all the band's production equipment. This can include lighting, video, staging and the band's instruments. A variety of speaker types is typically carried on the tour to accommodate the variety of seating arrangements various venues may provide.
Typically, a large line array is used to cover the main audience area and the farthest areas of an arena or stadium. Smaller line arrays are used to cover the outer sides and center of the audience area. Additional speakers are then also used on stage to cover the closest audience members. There are typically 2 to 7 or more separate loudspeaker arrays brought in and flown (installed) on the day of the show. As most systems are symmetric on the left and right, 1 to 4 or more arrays must be designed to fit their respective coverage areas. The arrays may comprise high, mid and low frequency speakers, as well as subwoofer (ultra low frequency) speakers.
With existing line array loudspeakers each box in the array can be set to a number of different angles relative to the adjacent box; smaller angles increase sound pressure level (SPL), larger angles increase vertical coverage. To get a general idea of the number of speakers required and location for array, acoustic modeling software is used to roughly “draw” the venue prior to the show. This initial look provides a starting point for future modeling, but not the actual angles or orientations of the speakers that need to be implemented on show day.
To fine-tune the speaker angles for the actual performance, a system engineer will arrive early in the morning at the venue to measure the dimensions of the room (typically with a laser range finder), and verify the actual suspension locations and trim height limitations. The venue configuration will then be modified in the modeling software and appropriate array angles and trim heights are chosen. This work must be completed before the loudspeakers can be flown (installed) in the venue.
The loudspeakers are then flown in the venue. Flying each array is a labor-intensive process. Large format loudspeakers typically weigh in excess of 200 lbs. Inter-cabinet angles must be set between each cabinet, typically at more than one point per cabinet. If angles are set incorrectly or the trim height is incorrect, the system could have non-ideal coverage, or worse, not cover the entire audience. Once all the arrays are flown, connected and powered, the system technician will take acoustical measurements of the system to see how the performance matches their acoustic model. If performance is very poor and time permits, an array might be brought down and reconfigured. However, if time does not permit, typically only system equalization and array alignment delay can be adjusted to improve performance. In extreme cases at least some loudspeakers are unplugged to modify coverage.